1. Field of the Invention
The present invention relates to a support rod structure, in particular to a press-fit extendable support rod.
2. Description of the Related Art
With reference to FIGS. 13 and 14 for a structure of a conventional support rod 8, the conventional support rod includes an inner bushing 81 and an external bushing 82. A supporting portion 83 is disposed individually at both ends of the support rod 8, a base 9 with an opening disposed at a joint position of the external bushing 82 and the inner bushing 81, and two locking plates 91 are extended radially from the bottom of the base 9 for fixing the external bushing 82. A handle 94 is pivotally coupled to the base 9, and a latch 92 is disposed at a front end of the handle 94, and a plurality of serrations 93 are formed at an end of the latch 92, such that the handle 94 can be pressed down to push each serration 93 into a latch hole 811 of the inner bushing 81 to adjust the extended length of the inner bushing 81.
In the whole process of adjusting the inner bushing 81, a front end of a grabbling hook 951 of a pawl 95 is abutted by a torsion spring 96, so that the grabbling hook 951 can be embedded into the latch hole 811 at an external periphery of the inner bushing 81 to maintain the position of the inner bushing 81 and prevent the inner bushing 81 from falling down.
In general, the grabbling hook 951 can be embedded into the latch hole 811 to achieve the positioning effect after the support rod 8 is adjusted to an appropriate length. However, this structural design of the support rod requires manufacturing the latch holes 811 in the manufacturing process of the inner bushing 81, and thus incurs a higher manufacturing cost. With the consideration of the deformation of the latch holes 811, it is difficult to enhance the rigidity by thermal treatment. Undoubtedly, the strength of the support rod is poor, and the grabbling hook 951 has to bear the acting forces coming from both ends of the support rod 8, and thus the grabbling hook 951 will be damaged frequently by the load. Obviously, the structure of the conventional support rod 8 has a disadvantage on life expectancy.
In the whole process of adjusting the extended length of the inner bushing 81, the serrations 93 of the latch 92 and the latch holes 811 are engaged with each other, and thus a fine-tune adjustment cannot be made since the length adjustment is limited by the teeth spacing. Particularly, such support rod 8 is used frequently for fixing goods in a container truck, but a fine-tune adjustment cannot be made and a small gap may be formed, so that the goods may get loosened or even fall down easily by the shaking forces occurred during transportations. This fine-tune adjustment issue creates tremendous troubles to users.